Encyclopedia · botanical
Black seed oil
Black seed oil's hair reputation rests on animal work and a tiny open-label lotion study, with no independent controlled human trial.
What it is
Black seed oil is the pressed oil of Nigella sativa seeds, best known for the compound thymoquinone. It is sold as a pure oil, in blends and in scalp lotions.
How it works
Proposed mechanisms (antioxidant, anti-inflammatory, follicle protection) come from rat work and general pharmacology. None has been shown in human scalp tissue.
What the studies show
- The reputation rests on a rat study of chemotherapy-induced hair loss and a small open-label study of a 5% oil scalp lotion over 28 days in 22 people, which reported less shedding and higher density with no control arm and links to an ingredient supplier.
- A systematic review of 8 studies found no controlled trials of natural ingredients for the scarring condition central centrifugal cicatricial alopecia. Ezekwe 2020
- Web summaries mention a 2013 study of a 0.5% oil lotion in women with telogen effluvium, but the paper could not be found, so it is not counted.
How it's used in studies
Rats received topical oil or a 5% decoction. The small human study used a 5% oil lotion once daily for 28 days.
Side effects and safety
No adverse reactions were reported in the small lotion study. Patch-test any new topical oil.
Bottom line
Weak evidence. It is fine as a conditioning oil if you like it, but do not use it in place of proven treatments. The only human data are short, open and commercially linked. A randomized, vehicle-controlled trial from a group with no commercial stake is needed.
Studies 1
Ezekwe N et al. The use of natural ingredients in the treatment of alopecias with an emphasis on central centrifugal cicatricial alopecia: a systematic review. J Clin Aesthet Dermatol. 2020
Tested: natural ingredients including black castor oil
Result: No clinical trials of natural ingredients for central centrifugal cicatricial alopecia were found.
Read the study ↗Related
- Castor oilCastor oil is a thick sealant that suits dry hair, but no controlled human trial shows it grows hair, and in rare cases it has matted a whole head of hair irreversibly.
- Rosemary oilRosemary oil became the internet's "natural minoxidil" from one small 2015 trial that had no placebo group and has never been replicated.
- Onion juiceA 2002 Iraqi study found crude onion juice regrew hair in patchy alopecia areata, but the control was tap water, the groups were small, and it was not shown for pattern hair loss.